Successfully complete all levels on the Hard difficulty setting to unlock Mega. He is Megaman in his basic helper clothes and attacks with a kick. To choose him, select Megaman at the character selection screen and use the menu that appears to play as him. -From: banetuh

Defeat a Robot Master in New Style mode using only the Mega Buster or Rock Buster to unlock that Boss as a playable character.

Charge Shot/Sliding move

Successfully complete the game on the Normal difficulty setting to unlock the Charge Shot/Sliding move.

Alternate title screen

Defeat any Boss in New Style mode. Use that Boss as your character and load the game to have the corresponding person at the title screen. Defeat all Bosses in New Style mode and select Megaman as your character to have all characters appear.

Misspelling

Successfully complete a level on the Normal difficulty setting. Sometimes Roll will say "Try your best on the next stage kay." instead of "Try your best on the next stage okay."